Help with howdens pan drawer rail catch pls

Hi.

I am fitting howdens kitchen. I have built the standard 900mm 3 drawer
I have fitted the runners.

Now I have runner reinforcement catches to fit.

What is the purpose of these other then hit the back panel (potentially weaken and already marked) to stop runner catch instead? Are they necessary and has anyone else fitted them.

Do they go on all drawers or just the top small one?

Any advice appreciated

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